Several approaches to combine the benefits of vertical or short takeoff and landing like that offered by a conventional helicopter with cruising performance superior to that of a conventional helicopter have been tried in the prior art. One approach produced tilt rotor designs such as the Bell/Bowing Osprey and Eurofan. In these designs, the aircraft take off and land as helicopters through the use of driven rotors and cruise as airplanes by tilting the rotors so that their axis of rotation is horizontal and the rotors provide thrust instead of lift. These aircraft can thus exceed cruising speed of conventional helicopters but cannot exceed the cruising speeds of other turboprop aircraft. One way to overcome this limitation is to provide a tiltable rotor aircraft with jet propulsion and somehow stow the rotors during wing borne, jet propelled flight. Prior art aircraft of this type, however, have suffered drawbacks in that the rotors are driven and therefore require complicated machinery which adds weight to the aircraft and, when stowed during wingborne cruising flight, cause excess drag and change the center of gravity of the aircraft.